Posted
by
samzenpuson Sunday April 29, 2012 @04:45PM
from the southpaw-statistics dept.

Hugh Pickens writes "Representing only 10 percent of the general human population, scientists have long wondered why left-handed people are a rarity. Now a new study suggests lefties are rare because of the balance between cooperation and competition in human evolution and a mathematical model was developed that predicts the percentage of left-handers by sport based on each sport's degree of cooperation versus competition. 'The more social the animal—where cooperation is highly valued—the more the general population will trend toward one side,' says study author Daniel M. Abrams. 'The most important factor for an efficient society is a high degree of cooperation. In humans, this has resulted in a right-handed majority.' If societies were entirely cooperative everyone would be same-handed, but if competition were more important, one could expect the population to be 50-50 because cooperation favors same-handedness—for sharing the same tools, for example while physical competition favors the unusual. In a fight, for example, a left-hander would have the advantage in a right-handed world. The mathematical model accurately predicted the number of elite left-handed athletes in baseball, boxing, hockey, fencing, and table tennis (PDF)—more than 50 percent among top baseball players and well above 10 percent (the general population rate) for the other sports. For other sports like football or hockey where team cooperation is paramount, it is ideal for all individuals to possess the same handedness. For example, in football, blocking schemes are often designed to protect a quarterback's blind side. As a result, it is beneficial for all quarterbacks on the roster to possess the same handedness to minimize variations of the offensive sets. 'The accuracy of our model's predictions when applied to sports data supports the idea that we are seeing the same effect in human society.'"

Why isn't everyone left-handed? That too would be beneficial in a cooperative society (shared tools). Maybe millions of years ago, the left-handed tribes died out. (Maybe they called themselves Neandertals.)

Why isn't everyone left-handed? That too would be beneficial in a cooperative society (shared tools).

This probably reflects the assymetries in the human body (heart on one side, one lung smaller, etc). Anyway, if all was in reverse and the majority were left-handed, you'd be here asking "Why isn't everyone right-handed?":).

- you're half-way there - just chop off the other one, and you'll be equally proficient with both (for some very low value of "proficient").

Kind of like the guy who found Bizarro Genie, who grants only one wish, and it never turns out like you expect. He wished for "a schlong so long it would hit the floor" - so the Genie cut off both his legs!

Why is there no mention of genetics? It's common knowledge that many people who were naturally Left Handed were forced to switch to be Right Handed back in the day. The whole shared tools is hog-wash. How many tools do you know of that depend on handedness? I can think of only a few, and none that are important: computer mice, modern fencing weapons, golf clubs.

Writing, scissors, buttons, car shifter (first few I thought of in 10 seconds).

In particular, writing: It's designed that right-handers are dragging the writing implement behind their hand in a smooth gliding motion. For left-handers we're smashing the point into the page in front of our hand, making it highly variable and irregular (a non-equilibrium), and then also smearing the hand over what we just wrote. Truly a pain. That's specifically the reason why my uncle (for example) was forced to switch by my grandparents tying his left hand behind his back.

And personally, I think that writing is the most important of all human tools.

Writing the way we do is because we are right handed. Earlier are left handed, because we chiseled it out of stone. That is easier from right to left. At least that is what I learned in school.However that does not explain writing from right to left in other languages. e.g. Arabic.

It is also the reason schools have the desks placed so the light comes in from the left si during writing you have more light.

You've got to see where Arabic alphabet comes from. It is an ancestor of the Aramaic alphabet, which itself was derived from the Phoenician one, which was incised with a stylus, which is, as you have mentioned, easier from right to left. Later, ink writing was introduced, but the writing system was already established. To make ink writing from right to left simpler, Arabic script was introduced, which started as a cursive Aramaic (more or less, there were more intermediate steps) and developed into what we

I practised writing right to left and in reverse as Leonardo Da Vinci was known to do, and it felt a bit wierd at first, but eventually it became easier. Obviously I didn't continue past satisfying my curiosity, because nobody would be able to read it easily.

My dad once asked his professor about how to format an assignment, to which the professor replied "I don't care if you do it upside down and backwards, as long as you do it." Well, you can guess where that led to.

After struggling through reading it, he gave my dad an A and made an announcement to the class that homework would no longer be accepted upside down and backwards.

Correct me if I'm wrong but that's where it is due to which side the driver sits, which in turn is due to which side of the road people drive on, which usually dates from the days when people rode horses (which don't have gears).

AFAIK the Nips, Limeys and Jaapies have roughly the same percentage of caggies as Americans do.

Car shifter isn't handedness. Otherwise, you are insinuating that drivers in the UK are left-biased. As someone who has driven on both sides, handidness doesn't matter for shifting. It isn't fine motor skills. You might as well complain about how doors are hung, and that's something that even the off hand is perfectly fine with.

I wasn't talking about how they got that way. That's irrelevant to the topic. The question was one about actions/tools that have some advantage/disadvantage based on handiness. Shifter was listed. Given the large number of people driving on one side or the other (or both, in some countries), there isn't any handiness link that can be drawn. Lefties aren't more likely to crash in the US, and righties aren't more likely to crash in the UK.

I'm sorry, but that's totally bogus. Most people who owned a horse (unlike a sword, horses naturally reproduce) didn't own a sword. According to your theory, the majority would want to ride - or walk - on the "wrong" side to be harder to target.

The fact is that we don't know why some countries and cultures got into the habit of "everyone on the right" and others "everyone on the left" - but it has nothing to do with left- or right-handededness.

The drive-on-left rule dates back to ancient times with the first real roads. It became a custom to make passing easier in travel, which was later invoked as law by the Romans and then the Pope. The modern use stems largely from the British colonization and the crown's ruling in 1773 requiring travel on the left. It is said that this was due to the ability of a horseback rider to hold the reins with the left hand and greet or defend themselves with a sword from oncoming travelers with

The correct way to write is to position the paper and the hand so that the hand is below the line of text being written. Nobody should be dragging their hands through previously written text, regardless of handedness.

Define "left-handed" or "right-handed". You can't come up with an unambiguous definition of either.

The only real definition we have is that "right" is the handedness of the majority of the human population. If the whole population was actually "left" handed as we now understand it, they would be right handed.

The short version of this post is, if you ever meet a perfect version of yourself constructed by aliens from radio transmissions, don't shake their hand.

if you ever meet a perfect version of yourself constructed by aliens from radio transmissions, don't shake their hand.

For those who don't know, this refers to a story in the Feynman Lectures on Physics. Here's my version; I've taken some liberties.

Imagine you're on the phone with an alien who speaks English, except they don't know what "left" and "right" mean. You want to explain it to them so they know which tentacle they should use to shake the right-handed President's hand if they should ever meet. The alien can be anywhere in the universe, so you can't refer to stellar positions or similar, leading you to devise an experiment for them to perform.

Your initial attempts use gravity, electricity, and magnets, but you notice each experiment comes out essentially the same if you swap "right" and "left"--for instance, you could give the alien instructions for making a clock in hopes of defining "right" using clockwise rotation, except if the alien made the clock exactly backwards by reversing the notion of "left" and "right", they wouldn't be able to tell. A particle physicist happens by and tells you about a magical experiment involving the weak nuclear force that *does* distinguish left and right inasmuch as the experiment fails if the alien screws up "right" and "left" and succeeds otherwise. (For the curious, some more details here [lbl.gov] and here [wikipedia.org].) Great, problem solved.

"But wait!" the physicist says. "The alien needs to use regular matter instead of antimatter in the experiment. The results will be reversed otherwise! Come to think of it, I have no idea how to tell them the difference between matter and antimatter. If you ever meet them and they start trying to shake your left hand, RUN, since the alien will be made of antimatter!"

Luckily, the physicist has since discovered another clever experiment which the aliens can use to differentiate between what we call matter and antimatter. There's a certain type of particle that can transform into it's antiparticle and back again. But the catch is that one of the transformations will happen more often than the other. That means that even if the alien swaps matter for antimatter they will still be able to tell which is which by looking at which transformation dominates. (More details here [wikipedia.org])

"Now," the physicist admits "this all assumes that the aliens haven't swapped the direction of time on us as well! Buggers might just have effects preceding causes." (See CPT symmetry [wikipedia.org])

The model in the paper specifically allows for two possible equilibria: one in which right-handed people dominate, and one in which left-handed people do. We just happen to be in the right-handed equilibrium (by chance).

Don't overthink it -- probably putting the vital heart further away from the hand that does most of the work (and fighting) gave those organisms slightly higher survival rates, especially with respect to danger, since it was less likely a bite, punch, whack, or, hell, a severed artery in the arm, for that matter, would cause the heart to stop.

I'm not ENTIRELY convinced, what about situations where it is advantageous for people to have opposite handedness for optimal cooperation? There seems to be a built-in assumption here that different-handed assortments of people will always have more problems working together. I'm not sure there's a practical way to test this as a general thing though.

Where would opposite hands lead to greater cooperation among primitive man?

I think the point is that left-handed people would need special left-handed spears, knives, et cetera. If they lost their special tool they couldn't just grab a friend's right-handed version, so they'd be left weapnless and get eaten/killed by the lion before they had a chance to procreate. Thus leftie genes would become rare in homo sapiens.

spears, knives and early swords had no handedness, which in the case of swords is limited to the form of the hilt, which in the case of a modern basket hilt is handed. and remember that in practically all the history of fighting, the relative size of the population gave an advantage to lefthanders, since the simple probability of meeting a left hander was too low for every right handed fighter to be adequately prepared, while the opposite is false, since left handers had plenty of practise working against

Eh, I have yet to meet a firearm that gave me any more than the most trivial problems. Certainly left-handed firearms are nice, but in a practical sense both sorts work fine. Working the safety on a pistol quickly is probably the least convenient feature of wrong-handed hand guns.

Eh, I have yet to meet a firearm that gave me any more than the most trivial problems. Certainly left-handed firearms are nice, but in a practical sense both sorts work fine. Working the safety on a pistol quickly is probably the least convenient feature of wrong-handed hand guns.

My father is right-handed, but shoots leftie. And he postively hates bolt-action rifles for that reason - operating a bolt from the wrong side is painful, at best.

It isn't a big deal. Most everyday items don't favor one hand or the other. Spears, knives, and even swords pretty much fall into this category, as do quite a lot of other tools. Scissors and similar cutters are sort of an exception. So chances are this wasn't a really large problem. In a pinch you can just use things right-handed (and most lefties are less hand-polarized than righties, maybe do to the convenience of being able to use either hand, for instance I'm perfectly happy doing many tasks with eithe

I'm neither left-handed nor right-handed (but I don't consider myself purely ambidextrous, either). I tend to favor my left hand for non-handed implements and tend to favor my right hand for handed implements. And I can tell you that the items you listed are not handed unless constructed to be so (curve of the handle).

However, I think the study failed to take into account that certain sports (such as golf and bowling) don't involve cooperation but should have a decided advantage for lefties. In golf, the

Where would opposite hands lead to greater cooperation among primitive man?

Think of a group of people rowing a large canoe with some rowing on the left and some on the right. Think of a group of people carrying the canoe. Think of sneaking up and surrounding an animal with some going to the left and others to the right. Think of cooperating in a fight against the neighboring tribe where it helps that your opponent doesn't have a pretty good idea which is your stronger arm. Think of buiding something whe

There is no reason a left-handed person and a right-handed person would have better luck flanking/attacking an enemy or prey than a pair of same-handed people.

If you have ever actually propelled a canoe, you would know that which side you paddle on does not matter. All steering and control should be done from the same side of the canoe(C-stroke and J-stroke) - you shouldn't be switching the side you paddle on to steer, or using an oar like a rudder.

I'm not ENTIRELY convinced, what about situations where it is advantageous for people to have opposite handedness for optimal cooperation? There seems to be a built-in assumption here that different-handed assortments of people will always have more problems working together. I'm not sure there's a practical way to test this as a general thing though.

I agree, the theory is weak.

Using sports as a model for why handed-ness exists is putting the cart before the horse. That Baseball was able to capitalize on left handed pitchers throwing to much more common right handed hitters is a rather late innovation in the annals of human endeavor.

Further, very few tools existed in historical times where handedness mattered at all. A wrench or a hammer or a spear have no handedness. Only much later were tools invented to meet the needs of the majority or users, which is why there was a tendency to put controls on power tools on the right.

The whole thesis mistakes cause for effect, suggesting tools and games we invented had something to do with what made us what we are. Whether our ancestors threw the spear, or picked the berry right or left handed couldn't have mattered at all.

For this to have any relevance he'd have to show that handedness was somehow genetic (right-handed parents had right-handed children) or determined soon after birth and influenced by the parents (right-handed parents taught their children to be right-handed unconsciously).

Then those right-handed parents were more successful in the cooperative culture than the left-handed people.

The article specifically cites evidence for an important genetic component of handedness, and the model is constructed around that evidence. The authors didn't have to 'show' this, as it has already been shown.

Perhaps you are confusing evolutionary modelling (a mathematical technique which describes very general processes of information transfer) with theorising about human origins (an empirical investigation which sometimes uses evolutionary models, along with other sorts of models and lots of physical evidence).

This paper is an example of the former, not the latter. It argues that, because there is a process of 'selection' involved in athletic try-outs, it may be possible to apply some evolutionary models to ex

I'm having a little difficulty with the idea that cooperation required same-handedness to the degree that it largely influenced evolution in pre-literate societies. Tool use is cited; I have never seen an axe, hammer, knife or shovel that was not largely symetric in design.

The sports bit is interesting, but probably a red herring. Cooperative sports like football etc. were not played by professionals hundreds of years ago, and they didn't have every detail of the game worked out and practised beforehand.

"Cooperation favors same-handedness—for sharing the same tools, for example. Physical competition, on the other hand, favors the unusual. In a fight, a left-hander would have the advantage in a right-handed world."

This is simply taken axiomatically as a starting point for the study. I see no indication that it was determined by any sort of analysis. I'm not even sure such an analysis is feasible. You'd have to know what activities people carried out in prehistoric times, how, and what the value of cooperation was for each one. There could be various advantages and disadvantages of same or opposite handedness depending on the activity, etc. The entire concept of their study rests ENTIRELY on the validity of this same-handedness is better for cooperation proposition. I'm not saying it is untrue, but without demonstrating it to be true and to what degree I cannot see how any meaningful conclusions can be drawn.

but without demonstrating it to be true and to what degree I cannot see how any meaningful conclusions can be drawn.

Well, if the model predicts reality accurately, one concludes the premises are plausible or likely. It's not the greatest form of evidence, but it's enough for many purposes. I've seen physicists ignore the lack of mathematical rigor in their arguments, and as far as I can tell the justification is the same: the results are pretty good, so the steps taken must have been correct.

For example, when two cars approach each other on a road from opposite directions, always stopping for negotiating passingeach other would be cumbersome. That is why most countries have right-sided traffic.

Bit of a non sequitur. Why does it matter which side it is, as long as it's consistent?

That's how I learned pool. I play leftie, as I was taught mirror of my grandfather. But as an adult, I've gotten more practice righty, so that I can switch for the shots that would be easy as a righty and very hard leftie.

Golf is slice-prone because instructors don't know how to teach it. A tiny amount of physics makes it simple. The shaft isn't centered. So the club face will always "open up" when the ball is struck. This directs the ball a little to the right and puts a spin on it that will have it

Handedness has nothing to do with hands. It's whether the right or left brain is dominant. There are right brain dominant people who also happen to use their right hands, even though their left eye, or left foot is dominant.

cooperation favors same-handedness—for sharing the same tools, for example

I'm struggling here to think of a primitive tool with handed-ness built into it. Anyone?

for example while physical competition favors the unusual. In a fight, for example, a left-hander would have the advantage in a right-handed world.

Doesn't know much about ancient warfare. Good luck running a phalanx or pretty much any massed swords -n- shields combat with some people randomly swapping sword and shield hands. Half your shield protects your buddy to the left, kinda like half of the shield of your buddy to the right partially protects you...

Of course if you're not one of those religious extremist types, the majority of human evolution happened long

>>>>> In a fight, for example, a left-hander would have the advantage in a right-handed world.>>>>Doesn't know much about ancient warfare. Good luck running a phalanx

In a competitive species the phalanx wouldn't even exist, because the humans would not cooperate with one another. Thus there'd be no need disadvantage to being either right or left, and the genes would be split evenly 50-50.

I'm struggling here to think of a primitive tool with handed-ness built into it. Anyone?

Not exactly primitive but everything in ancient Roman and Greek culture was built around everyone being right handed. Even the language reflected the value of being right handed compared to being left handed. They would slap students' left hands, even the great Caesars, to get them to learn to be right hand dominant.

The Latin (Roman) word for 'right' was 'dexter'. It's where we get the words dexterity, dextrous, and ambi

OK the greek and roman stuff happened well after 99.999% of human evolution had ironed out all that stuff. They're a lot closer to me than my ancestor 200K yrs ago (or whatever) back when we selected for handedness.

BTW the sinistra business is all about shaking your fren-imes hand with the right hand, holding real tight so he can't get away, then stabbing him in the gut with a dagger held in the left hand.

The monkey-see monkey-do thing is relevant to the pre-historical era. That is a good argument. That

I'm struggling here to think of a primitive tool with handed-ness built into it. Anyone?

Any kind of axe or hammer or adze whose haft is made from a found object such as tree branch would qualify.

Such hafts are never perfectly symmetrical, and they are held asymmetrically. A good tool will exploit the natural shape of the haft so as to conform to the user's handedness. The center of effort of the tool as well as the attack angle of the blade will be set accordingly. It's usually obvious in the insta

You joke, but that was literally true for me w/ regards to handwriting. Then one day my second grade teacher saw me switching hands and freaked out. She made me sit on my left hand for the rest of the year and had the colossal gall to tell me that someday I'd thank her for it. When my doctor learned about it at my next annual physical, he was pissed off beyond belief. He didn't cuss, but he kept muttering about "superstitious morons" and "subjecting kids to the prejudices of idiots", or words to that effect.

Fortunately the only thing impacted was my handwriting. Fifty years later my left-handed writing still looks like a first-grader while my right-handed writing got arrested at a second grade level. But I'm one heck of a typist, when I played soccer I did equally well on either left or right wing, I'm popular at dinner parties because I can accommodate whoever I am seated next to without bumping elbows, and my wife thinks I'm a very versatile fellow.

Fifty years later my left-handed writing still looks like a first-grader

I didn't have a teacher or anyone else force me to stop writing with my left hand, but I've arrived at similar results through a different path. In Brazilian schools they drilled cursive handwriting on you right up until 4th grade or so. I would typically choose my right hand because when writing left-to-right, it's easier to see what you're doing. However, when my wrist got tired, I'd switch. Eventually they stopped giving us so many handwriting practice assignments, and as a result, I stopped getting

Just a few years ago, a Canadian study using baseball stats (because they tracked handiness closely) concluded that lefties were far more likely to die, ( http://www.nejm.org/doi/full/10.1056/NEJM199110033251412 [nejm.org]) this was later shown to have suffered a seemingly paradoxical sampling error (not controlling adequately for those that didn't die). Then there was another study that concluded that left-handedness was likely the result of anoxia in the womb ( http://www.sciencedirect.com/science/article/pii/002839327390050X [sciencedirect.com]). It was discounted for similar sampling error problems. Neurological "wiring error"; perhaps a mutation with few consequences; advantages in the mathematical world (presumably via having a screwy mindset); Language disadvantages; Language *advantages*; high proportion of left-handed (possibly suppressed) American presidents http://www.anythingleft-handed.co.uk/presidents.html [anythingle...nded.co.uk] (Clinton, Bush, Obama... ). So... run a elaborate predator/prey model applied to sports and see an advantage for the 10% that are different; sounds like rediscovery of Perato distribution to me, http://en.wikipedia.org/wiki/Pareto_distribution [wikipedia.org] I'm just not convinced that there's been a proper scientific approach to this issue to date, and until then i'm still stuck with a twisted spine in most college classrooms.

If a child learned to type before they learned to write, would they ever consider which "handed" they are?

I'm left handed, but aside from handling pens (which these days don't do on a daily basis) I do pretty much everything with both hands equally. When I was a kid alot of todo was made of getting me a left handed baseball glove, left handed scissors, and even a left handed violin. None of those things were very useful. I can catch, cut, play, even shoot with both hands, more or less evenly. (I actually

. . . but before there were organized sports, people had to deal with certain personal matters. They also had to physically interact. As one once said, "I don't eat where I shit." Of course, you might argue that, "One hand washes the other." That is true, but every shithole did not come with Purel, a bidet, or even water. There are other practical reasons for using one hand for one thing and the other for something else.

Frankly, I doubt if being left-handed or right-handed is genetic. Perhaps it is hereditary in the sense that you learn from birth based on how others use their hands, and it would be easy to use such behavior to perpetuate a trend. For example, everyone born in a Mandarin-speaking village begins to speak Mandarin without any formal training. Or most people use their hands to eat instead of their feet, which anyone born without hands can tell you is quite doable.

As others have pointed out, society can use commonalities to its advantage, which would re-enforce such trends.

The idea that it's beneficial for every player on a hockey team to be same-handed shows quite an ignorance of the game. There is a left-wing position and a right-wing, and being able to either protect the puck from a defender, and/or have the best possible angle to shoot on net, depends very much on whether the player shoots left or right. This is further complicated by players who choose to shoot left despite being right-handed (see this blog post here [darrenbarefoot.com], I couldn't find a better source)

I haven't RTFA (obviously), but it sounds like those fellas hammered a model onto a data set and attached a nice simplistic explanation on top of it.

The reason many lefties excel in some sports is due to the element of surprise their left-handedness gives them. Finding a simple formula to determine lefties percentage depending on some arbitrary criteria of cooperation/competition, which is an enormously complex subject in itself, sounds like complete nonsense.

I browsed through the PDF{blockquote}In Table S1, the predictions for the fraction left-handed were generated using an estimate of the ideal equilibrium lfor each sport. The appropriate value for l depends primarily on the degree of cooperation c for the sport. Thisparameter is dicult to estimate in sports that possess clear cooperative and competitive elements. However, in orderto observe xed points other than l = 1/2, c must exceed a threshold that appears to be relatively high for thetypes of transition

As someone who knows a little bit of mathematical modeling and statistics, I have to point out that they did not predict the percentages, since they already were known! The correct term would be retrodict.

Can this article explain why there are so many left-handed people at my company, especially in IT? I've been in meetings of 8-10 people and noticed that _everyone_ in the room is left-handed (~1000-person company). It seems statistically unlikely.

Anyone can be ambidexterous (minues amputees) the real reason most people are "single" handed is the simple fact that most people don't bother learning to use the other hand once they've mastered most common tasks with either the left or the right hand.

Don't believe me. Try this.

First try brushing your teeth every day using your off hand. Do the same with eating and simple things like going to the bathroom or shaving. After a month, practice throwing a ball with your off hand. Start writing after

Course design does play a part in how successful a golfer of a certain handedness can be, albeit more in amateur or developing golfers. Most amateur right-handers tend to slice a ball (curve to the right,) while left-handers hook the ball (curve to the left.) I'd be willing to bet there are more dog-leg-right holes than there are dog-leg-left holes.

I stopped playing golf a while back in favor of disc golf (it's free,) and the hole selection is even more biased. It's difficult for me (a left hander)